AutoCAD2013 IS different with regards to it's ability to "Save down" legacy drawings that DO NOT already contain AEC content, just as donande has described. This DID NOT happen before.
In the video below, the default template from AutoCAD2005 (dated Jan-24-2003) is opened, then saved by both AutoCAD2012, and 2013, clearly demonstrating that vanilla AutoCAD now adds new AEC content to everything it touches. The hardship this causes for other users is obvious.
donande, feel free to use this video to demonstrate to your support guy that he's wrong about the file already containing AEC content, and also that this is NOT how it's always been.
**edit* updated the video
Interesting. I believe you. Not sure that the acad.dwt from 2003 contains no AEC object but it doesn't matter. There could be something else going on with respect to the base view, section view, and detail view object that might get installed at open.
I actually use AutoCAD Architecture and experience none of the problems you have demonstrated. I have a video link with 2013 (as autocad) saving back to 2007 and then opening with autocad architecture 2012 as autocad. No warnings at all. This doesn't contradict your experience but shows that it isn't universal.
Something might be happening in base AutoCAD that is not happening in AutoCAD Architecture. For example, when I drew a solid and use the viewbase, section and detail views and saved back I got the same message you did at 2012 open.
Did you check to see if the version conflict message is supressed in 2012?
When you run ACA as AutoCAD, do you still have to use Object enablers for ACA content, or is that support already included in your AutoCAD as a result of being a child of ACA?
Here ya go Dean.... the lsp apparently doesn't process .dwt's (the source file) but as you can see, that lisp does not detect any AEC in the file saved by AutoCAD 2012, ..... whereas the file saved by AutoCAD2013 DOES
1) Good catch. Proxy notice dialog is turned off by default I think. With ACA, there is typically no way to avoid getting AEC object in the drawing. When I first started using it I experimented with using AECobjexplode and exporttoautocad but found that after being opened and saved again, enough came back to cause the same warnings.
Other than not getting the warnings, I haven't had any problems using or modifying these saved back files that do not contain AEC objects. The proxy dialog is triggered even when no graphical objects are present. This probably means that they are triggered by special layering and display features that are disabled anyway and not used by AutoCAD.
2) I don't know for sure but I assume that the enablers are active. I think enablers are a part of autocad base as well however.
Without the proxy dialog box nagging you, I doubt that you would even notice any usability difference between native drawings and those saved back. I would recommend just turning it off. If you run into anything that you cannot actually edit, then that would be a real problem.
To process a dwt file, just rename it to a dwg file.
My vanilla install of 2013 does not behave the same with regards to the AEC objects.
Warning messages are not supressed on my install. I used the acad.dwt that ships
with 2013 found at the following location
C:\Documents and Settings\JasonPiercey\Local Settings\Application Data\Autodesk\AutoCAD 2013 - English\R19.0\enu\Template
I receive no AEC messages of any kind when saving the default acad.dwt as a
drawing file and/or opening the file that was saved. My acad.dwt is dated 01/17/2012
Great, so now you know, 2013 adds to your file what that lisp considers AEC content, which are not backwards compatible. Ever. So I'm not sure what else you seek, other than a clarification of what these AEC objects are: you can't take AEC objects back to a lower DWG format remains a reality.
Post your DWT/DWG file if you wish for others to dissect, perhaps even an Autodesk'er so that they can try and explain where this content comes from.
I just tried the same thing with my vanilla 2013 and did not get the results that you had. I used 2013 to start a clean drawing from my 2012 template and saved to 2007 format, no error message upon saving. Open saved dwg with vanilla 2008 and did not get any AEC warning.
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